Distillation technology, the most widely used unit operation in the chemical field, although has considerable advantages, meanwhile demands relatively high energy consumption and investments. The energy consumption of distillation accounts for more than a half the total energy consumption of a chemical process or the like. Thermally coupled distillation, a complex distillation approach proposed in the 1940s and 1950s, can reduce irreversible effective energy consumption in a procedure, and thereby reduce energy consumption of the procedure. As has been proved both in theory and practice, a thermally distillation column enables about 30% of decrease in average energy consumption as compared with a conventional distillation solution. Thermally coupled distillation typically refers to full thermocouple distillation. In connection with distillation comprising separation of a three-constituent mixture or separation of a mixture to obtain three products, a thermally coupled distillation column can be a Petlyuk distillation column or a vertical partition plate distillation column. Although the two are thermodynamically equivalent, investments on devices can be further cut down when the vertical partition plate distillation column is used. Nevertheless, the partition plate distillation column, with a pre-separation column and a main column integrated into one column shell, is regarded as one special case of Petlyuk column by some people. In the vertical partition plate distillation column, a vertical partition plate is arranged in the distillation column to divide the distillation column substantially into four parts, including an overhead section, a bottom section, and a feed section and an intermediate side-draw product section separated by the partition plate. Compared with a conventional two-regular-column sequence flow, the vertical partition plate distillation column can save 30-60% of energy consumption and about 30% of investments in devices, with increased operating capacity. Although a dividing wall column has prominent advantages as mentioned above, it took rather a long time for the concept of dividing wall column, which was first proposed in the 1930s, to be industrially used. This is mainly because wide use of the dividing wall column is blocked by lack of reliable design procedures and feasible operation and control solutions.
U.S. Pat. No. 4,230,533 uses liquid reflux powered by difference in liquid levels, which are regulated by means of a flow meter, wherein distribution of a vapor moving upwardly from the bottom of the column is regulated through by-pass conduit means, and vapor distribution is irrelevant with distribution of liquid reflux. U.S. Pat. No. 5,755,933 discloses a dividing wall column which has a partition plate extending to a top or bottom of the column, and respective condensers or reboilers are used for reflux. U.S. Pat. No. 7,267,746 discloses a control method of a dividing wall column, comprising feeding streams of different constituents from different portions of the column, so as to form liquid reflux control and regulate flow of the streams entering the column, with an overhead temperature as a regulation index. The above technologies have a common defect, i.e., inability of independent control of overhead liquid reflux and a rising vapor from the bottom of the column.